Hardening and stain prevention process in color photography



Patented Jan. 16, 1945 UNITED STATES PATENT OFFICE HARDENING AND STAIN PREVENTION PROCESS IN COLOR PHOTOGBAPHY Paul W. Vittum, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N Y., a I corporation of New Jersey 9 No Drawing. Application September 4, 1942,

Serial No. 457,326

) Claims.

This invention relates to photographic hardening baths and particularly to baths of use in color photography for hardening and preventing the staining of gelatin emulsion layers.

In processing color films having gelatin emulsion layers by means of color-forming development methods, it is usually desirable at some stage in the process to harden the emulsion layers of the film. For instance, in the color process disclosed in the prior U. S. Patent N0. 2,252,- 718, granted August 19, 1941, to Mannes et 2.1., it is convenient to harden the emulsion layers following color-forming development and prior to removal of the silver images with ferricyanide and hypo-solutions. I have found that the usual hardening solutions used for this purpose have a' deleterious effect upon thedye images which may be traced to the presence of sulfite in the hardening bath. from coupler compounds giving azomethine, in-

doaniline and indophenol dyes are particularly susceptible to attack by sulfite and the eiiect produced is a destruction of a portion of the dye It appears that dye images formed hardening bath contemplated by my invention.

Example Sodium acetate; "grams-.. 15.0 Acetic acid (28 per cent) cc 47.0 Boric acid ..grams 7.5 Potassium alum do 15.0

2o Water tocc 1000.0

image and rendering the remaining dye image unstable. Similarly, in processing color films having coupler compounds incorporated in the emulsion layers, constructed, for example, as

described in Jelly and Vittum U. S. Patent 2,322,- 027, granted June 15, 1943, Mannes et al., U. S.

Patents 2,304,939 and 2,304,940, granted Decembe: 15, 1942, it is desirable to harden the emulsion layers subsequent to color-forming development and prior to removal of silver from the films. With these films the presence of sulfite in the hardening bath adversely affects the dye images as described.

In processing the above films it is also observed that there is a tendency for stain to be produced in the emulsion layers when the color developed films are treated with ierricyanide or other oxidizing olutions used for the removal of silver from the layers. It is believed that this stain results from the oxidation of traces of the colorforming development compounds retained in the layers following color-forming development.

I have found that by the addition of acid to the hardening bath used prior to treatment of the above films with oxidizing solutions for the.

removal of silver, stain may be reduced. The acid apparently removes from the solution layer any color-forming developer compound extracted from the developer by. the emulsion layers. Therefore, no developer compound is available As shown, the baths of my invention may contain a butler compound, an organic acid, a gelatin hardening agent and boric acid. Instead of the particular bufier compound shown in the example, one may use other compounds of similar activity such as citrate, borate, etc. Similarly, other organic acids and gelatin hardening agents-such as chrome alum may be used in the formula. It is not necessary that the formula contain boric acid; however, the compound may be used where accelerated hardening is desired.

I will now describe a color process in which a bath of my invention is especially useful. A color film carrying sensitive emulsion layers containing coupler compounds and, if desired, crystalloidal materials as described in the Jelly and Vittum application above-mentioned, and in which the coupler compound for forming a cyan image in the red sensitive emulsion layer is, for example, an acyI-o-amihophenol, such as acetamino phenol, is exposed in the usual manner to a colored scene. Following exposure the film is developed in a color developer of the following Cyan, magenta and yellow dye images are thus developed in the respective emulsion layers. It is found that if the emulsion layers of the developed film are now hardened in a hardening bath of composition shown in the aboveexample prior to removal of silver from the layers, the dye images are not ailected and any color-forming developer compound in the layers will be removed; otherwise, a hardening bath, containing sulfite especially if applied prior to removal of silver will adversely affect the dye images. After hardening the emulsions the film is treated with ferricyanide and hypo solutions to remove silver and any silver halide'in the layers. Color negatives thus produced may be printed onto a similarly constructed color film or paper having coupler compounds incorporated in the emulsion layers, and the exposed photographic elements then developed with a color-forming developer of the above composition to form subtractive dye images in the respective emulsion layers. Then, in the manner of my invention, the emulsion layers are hardened with a hardening bath such as shown in the above example followed by removal of silver and silver halide from the element. A multicolor image which is a positive in respect to the original scene is thus obtained.

A color film constructed as described in the Marines et 2.1. U. 5. Patents 2,304.,939 and 2,304,940 above-cited may be processed in a similar manner to give a color negative which may be printed onto a, similarly constructed positive color film and processed as described to a color positive using the hardening bath before removal of silver and silver halide.

A film constructed as described in the above Marines et al. U. S. Patent No. 2,252,718 is processed as described therein using a hardening bath according to my invention as follows: after exposure, negative development, and reversal exposure and color-forming development of the respective emulsion layers, the film is treated with a hardening bath compounded as described under the above example, followed by removal of the silver images and silver halide using ferricyanide and hypo solutions. The hardening bath functions as above-described to harden the emulsion layers and to removecolor-forming developer compound from the'emulsion layers.

Color filmscontaining coupler compounds and, if desired, crystalloidaior porosity modifying materials as described in the Jelly and Vittum Pat- 'ent 2,322,027,- and Marines et al. Patents 2,304,939

and 2,304,940 above, may also be processed by the reversal process of color photography as follows using a hardening bath according to. my invention: after exposure of the dim it is developed to a blsck-snd-white negative in HQ developer, and then the emulsion layers are selectively reexposed and color developed to produce subtractive dye images in the layers. Following this, a hardening bath or composition, such as shown in the above example, is used to harden the emulsion layers and to remove any developer compound in the layers. Film is then-treated with ferrlcyanide and hypo solutions to remove silver and any silver halide in the layers.

As I have mentioned the dye images which are most adversely aflected by white in a hardening bath are those formed from coupler compounds yielding azomethine, indophenol and indoaniline dyes with. color-forming developers. Other coupler compounds giving the images espeassure Sebsclc acid dl-(ihydroxy aniilde) 2-hydroxy-4'-(3-phenoxy benzsmido)-diplienyl O I s or-[n-cocmcn N-n-butyl-Z-cyanoacetylnaphthaleue-7-sulianillde C sHil CBHIIOI!I S 0 in N-n-nmyI-ZeyanoacctyIcoumarone-S-(p-tcrt-umyI-sullanilldo p-tert-butyl phenoxyethyl-p-benzoyl aoetaminobcnzene sulfonatc It is apparent that the above description is merely illustrative of the various means of accomplishing the objectsof my invention and it is to be understood that the disclosure herein is by way of example and'that I consider as included in my invention all modifications and equivalents ralling within the scope of the appended claims.

What I claim is: v

1. In color photography, the method 0! processing a light-sensitive silver halide gelatin emulsion layer which comprises exposing said. layer, developing a dye image in said layer by means of color-forming development, prior to treatment with solutions removing silver from the layer treating said emulsion layer containing a dye image with a hardening bath free of sulflte comprising a photographic gelatin hardening agent, a bufier compound and an organic acid whereby the emulsion layer is hardened and any color-forming developer compound in the layer is removed without aiIecting the dye image,

and removing the silver and any residual silver a dye image with a hardening bath tree of sulcially susceptible to sulfite which dye images 13 fite comprising alum, sodium acetate, acetic acid,

and boric acid whereby the emulsion layer is hardened and any color-forming developer compound in the layer is removed without affecting the dye image, and removing the silver and any residual silver halide from the layer.

3. In color photography, the method of processing a light-sensitive: silver halide gelatin emulsion layer containing a coupler compound which comprises exposing said layer, developing a dye image in said layer by means of colorforming development, prior to treatment with solutions removing silver from the layer, treating said layer containing a dye image with a hardening bath free of sulfite comprising a photographic gelatinhardening agent, a bufier compound and an organic acid whereby the emulsion layer is hardened and any color-forming developer compound in the layer is removed without afiecting the dye image; and removing the silver and any residual silver halide from the layer.

4. In color photography, the method of processing a light-sensitive silver halide gelatin emulsion layer which comprises exposing said layer, developing a silver image in the exposed layer, exposing the unexposed silver halide in the layer, forming a dye image in the exposed layer by means of. color-forming development, treating the layer with a hardening bath free of sulfite comprising a hardening agent for gelatin, a bufier compound and an organic acid whereby the layer is hardened and any color-forming developer compound in the layer is removed without afiecting the dye image, and removing the silver and any'residual silver halide from the layer.

5. The process according to claim '4 wherein the hardening bath comprises alum, sodium acetate, acetic acid and boric acid. I 6. In color photography, the method of processing a light-sensitive silver halide gelatin emulsion layer containing a-coupler compound which comprises exposing said layer, developing a silver image in the exposed layer, exposing the unexposed silver halide in the layer,- forming a '7. The process according to claim 6 wherein Y the hardening bath comprises alum, sodium acetate, acetic acid and boric acid.

8. The method of hardening a gelatin emulsion layer containing silver and a color-developed dye image, and removing any developing agent present in the layer, which comprises treating said 1 layer after color-forming development and prior to fixing,'with a sulfite-free bath comprising essentially a gelatin hardening agent, an organic acid, and a butler compound.

9) The method of hardening a gelatin emulsion layer containing silver and a color-developed dye image, and removing any developing agent present in the layer, which comprises treating said layer after color-forming development and prior to fixing, with a sulflte-free bath comprising essentially alum, acetic acid, andsodium acetate.

PAUL W. VI'II'UM. 

